This application is based on and hereby claims priority to Japanese Application No. 2002-109808 filed on Mar. 7, 2002, the contents of which are hereby incorporated by reference.
The invention relates to a spirit level, which measures precisely the inclination of a device such as equipment, which performs handling and precise processing of a wafer in a semiconductor factory.
Conventionally, a spirit level shows the inclination by measuring the location of air bubbles in a liquid. Alternatively, a spirit level detects inclination and presents a digital representation of the detected data by measuring the location of mercury within an enclosure.
A spirit level has a sensor to detect the level where the sensor is installed. A spirit level having a digital display indicates the inclination at a portion of the spirit level where the sensor is installed. Therefore, the user can easily know the inclination at the location of the sensor.
However, the above conventional spirit level simply displays the inclination at the part measured. Therefore, when it is necessary to precisely measure the inclination at two or more locations, a difficult problem is presented for the following reasons.
For example, it may be necessary to adjust the level on semiconductor fabrication equipment having a length of some meters. With conventional technology, a user adjusts the level at point A, using a spirit level. After that, the user adjusts the level at point B, which is apart from point A. While measuring the inclination at point B, the inclination at point A may change by natural phenomenon. Therefore, it was difficult to measure the inclination at both point A and point B precisely, and to precisely level the two points relative to one another.
The inclination varies based on natural phenomenon factor and other factors. For example, in connection with marine ebb and flow near the seashore, the level of a building foundation will shift with time. Moreover, if a portion of a building is heated, such as when sunshine hits one side of the building, the heated portion will expand, thereby changing the slope of the floor. Moreover, in a brittle foundation area, adding weight to the building, such as when new equipment is installed, may cause land subsidence.
In view of the changes, it is difficult to precisely adjust the inclination at both point A and point B using conventional equipment. That is, if the level at Point A is measured and adjusted, and then the level at Point B is measured on the basis of the adjusted level at Point A, there may be a change in inclination at Point A between the time of adjusting Point A and adjusting Point B. This makes precise measurement and inclination adjustment difficult.
One possible object of the invention is to precisely measure the inclination at two or more places.
The present invention provides an inclination sensor having a first inclination sensor, at least one second inclination sensor, and display to represent an inclination for the at least one second inclination sensor based on an inclination for the first inclination sensor. The display may represent the inclination for the at least one second inclination sensor as an inclination relative to the inclination at the first sensor. At least one of the inclination sensors may have a changing inclination. In this case, the display represents the inclination for the at least one second inclination sensor based on the changing inclination. The inclination sensors may be movable with respect to a remainder of the spirit level. In this case, the inclination sensors may be connected to the remainder of the sprit level with a cable or high frequency radio links.